1. Field of the Invention
The present disclosure is related to fish passage systems and methods. More particularly, the present disclosure is related to inflatable weir fish passage systems and methods.
2. Description of Related Art
It was recognized long ago that obstructions in rivers and waterways, such as dams, affect a fish populations' normal upstream and downstream migration practices. Fragmentation of rivers and waterways via an obstruction can and has resulted in the decline and in some cases a complete loss of fish species. Species such as steelhead, chinook salmon, suckers, American Shad, and River Herring are particular susceptible to declines from impassable river obstructions. The life history of species such as these requires that they migrate upstream to find suitable spawning locations. Thus, effective passage can be critical to the protection and recovery of many fish stocks.
A fish pass, also known as a fish way or fish ladder, is a structure designed to allow fish the opportunity to migrate upstream and continue when blocking structures are present in the water flow.
Several prior art fish passage systems have been proposed to assist these upstream and downstream migration practices. Common prior art fish passage systems including the rock-ramp fish way, the pool-weir passage, the vertical slot passage, the Denil fish way, and the fish elevator or lift.
The rock-ramp fishway uses large rocks and timbers to create pools and small falls that mimic natural structures. Because of the length of the channel needed for the ladder, such structures are most appropriate for relatively short barriers.
The pool-and-weir passage is one of the oldest styles of fish passages. It uses a series of small weirs or dams and pools of regular length to create a long, sloping channel for fish to travel around the obstruction. Effectively, the channel acts as a fixed lock to gradually step down the water level; to head upstream, fish must jump over from box to box in the ladder.
The vertical slot passage is similar to a pool-and-weir system except that each “dam” has a narrow open slot in it near the channel wall. This allows fish to swim upstream without having to leap over an obstacle. Vertical slot fish passages also tend to handle reasonably well seasonal fluctuation in water levels on either side of the barrier.
The Denil fishway uses a series of symmetrical close-spaced baffles in a channel to redirect the flow of water, allowing fish to swim around the barrier. Denil fishways need not have resting areas, although pools can be included in one to provide a resting area or to help reduce the velocity of the flow. Such fishways can be built with switchbacks to minimize the space needed for their construction.
The fish elevator or fish lift breaks provides a sort of elevator to carry fish over a barrier. With a fish elevator, fish swim into a collection area at the base of the obstruction. When enough fish accumulate in the collection area, they are carried into the river above or below the barrier.
The type of fish passage selected needs to take into consideration the different species of fish, since they have different physical and group characteristics. Unfortunately, the prior art fish passage systems have often not proven useful for multiple species of fish present in the same waterway.
Further, many of the prior art fish passageways have proven costly to install, maintain, and operate. Moreover, many of the prior art fish passageways, while effective for moving fish have not proven effective at controlling water level within the waterway, requiring a separate water level control system to be installed.
Accordingly, there is a continuing desire for fish passage systems that overcome, mitigate and/or alleviate one or more of the aforementioned and other deficiencies and/or deleterious effects of prior art fish ladders.